PURPOSE. Two façades having nominally equivalent sound insulation declaration, such as Rw+Ctr value, may have very different frequency behaviors leading to different spectrum of road traffic noise (RTN) indoors. Because spectrum affects annoyance of sound, spectrum may also affect sleep quality. Our purpose was to determine, how the spectrum of RTN affects sleep.

METHODS. Twenty-one participants slept three nights in a sleep laboratory in three different conditions: LF (low frequency prominence, 37 dB), HF (high frequency prominence, 37 dB), and Q (control, quiet, 19 dB). Conditions LF and HF were created by filtering an outdoor recording of RTN through two filters corresponding to two different sound insulation spectra but equal value of Rw+Ctr = 37 dB. Sleep quality wasmeasured both objectively (polysomnography) and subjectively (questionnaires).

RESULTS. Subjective sleep quality was worse in conditions LF and HF than in Q. Duration of slow wave sleep (deep sleep) was shorter in LF and HF than in Q. LF and HF did not differ from each other. After the experiment, most of the participants rated condition HF as the most disturbing for sleep.

CONCLUSIONS. High frequency RTN may be more adverse for sleep than low frequency RTN, but more research is needed.